1. Field
The subject matter disclosed herein relates to electronic devices, and more particularly to methods, apparatuses and articles of manufacture for use in a mobile device having a barometer or altimeter (these terms being used interchangeably herein).
2. Information
As its name implies, a mobile device may be moved about, e.g. typically being carried by a user and/or possibly a machine. By way of some non-limiting examples, a mobile device may take the form of a cellular telephone, a smart phone, a tablet computer, a laptop computer, a wearable computer, a navigation and/or tracking device, etc.
In certain instances, particularly with indoor navigation applications, it may be useful to determine an altitude level of a mobile device. This may be particularly useful in navigating multi-story environments in which a mobile device may be provided with navigation assistance data such as locations of transmitters, radio heatmaps, digital maps for display, routing maps, etc.
A mobile device may be determined to be located on a particular floor of a building using one or more wireless signal-based positioning techniques. In particular scenarios, it may be desirable to provide estimated locations of a mobile device to include an altitude level component. In a dense urban environment including multistory skyscrapers, for example, merely providing longitude and latitude components for a location in the absence of an altitude level component may be of limited utility for some services (e.g., emergency 911 services).
While obtaining a position fix from acquisition of satellite positioning system (SPS) signals in a rural or single-story suburban environment may provide an altitude level component of sufficient accuracy for most services, an SPS or other like signal-based position fix may not provide an altitude level component with sufficient accuracy or precision.
In certain implementations, a network carrier may populate a dense urban environment with low-power beacon transmitters and/or femtocells to assist subscriber mobile devices in accurately resolving an altitude level component of locations of the mobile devices. Such a deployment of low power beacon transmitters and/or femtocells may, however, prove too costly and/or provide for limited/sporadic coverage.
In another particular implementation, a mobile device may resolve an altitude level component of its location (e.g., as being on a particular floor of a building) by obtaining atmospheric pressure measurements using an onboard barometer and comparing such to a reference atmospheric pressure. However, atmospheric pressure tends to change over time, for example due to weather effects, and hence a reference atmospheric pressure (local to the mobile device) may need to be frequently calibrated. Rather than relying on remote devices to provide reference atmospheric pressure updates, it may be useful for a mobile device to determine a reference atmospheric pressure on its own, for example, through one or more barometer calibration processes which may identify a reference atmospheric pressure corresponding to a particular altitude level.